1. Field of the Invention
This invention relates to nozzles that are employed to spray fluids such as water that may contain nozzle clogging foreign substances and, more particularly, to a nozzle which is capable of self-cleaning such foreign substances.
2. Description of the Prior Art
Nozzles for spraying fluids are well known in the art and are frequently employed to provide a controlled spray pattern of liquids such as water. In most uses, nozzles may function for extended periods of time without maintenance since the fluid sprayed by the nozzles does not contain any foreign substances that cause adverse effects such as clogging of the nozzle. However, in some applications, nozzles may have a tendency to become clogged because contaminants that may be suspended in the fluid to be conducted by the nozzle may clog the fluid passageway in the nozzle. Such nozzle clogging is, of course, undesirable since the clogged nozzle must be cleaned before it is again in effective condition for its intended use.
Coal mines frequently have dust suspended within the air in the mine. Such dust is undesirable because it can create a health hazard to personnel within the mine that breaths the dust. Additionally, such dust may have an adverse effect on the operation of equipment within the mine. Such dust, however, is frequently difficult to remove from the air.
One such way to control dust within a coal mine is by spraying water through the air that contains the dust since a substantial amount of the dust will mix with the water and settle to the floor of the mine with the water. Spray systems are very effective in preventing dust from becoming airborne in a coal mine. The degree of effectiveness of the spray is dependent on the rate of flow of the water and the coverage, or area, over which the water is sprayed rather than the pressure of the water itself. Water sprays may also be effective in pushing or drawing airborne dust away from the area where personnel are working.
It has been experimentally determined that the most effective spray systems reduce inhalable size dust by about 60%. When such spray systems are used in conjunction with proper ventilation systems, almost complete elimination of airborne dust from the vicinity where personnel are working can be achieved.
Water spraying nozzles are frequently employed to spray water to control the dust. However, such nozzles tend to become clogged by airborne contaminants and contaminants entrained in the spray water. Studies have determined that most contaminants come from the water employed to produce the spray. Most contaminants are in the form of coal, although pipe scale, sand and some stone may also be present. Also, studies have shown that about 1/3 to 2/3 of water spray systems may be clogged at any given time within a coal mine and that each system may become repeatedly clogged during a single work shift. Further, previous solutions to such clogging conditions required either a lengthy cleaning process or replacement of part of the spray system itself. Both solutions resulted in considerable system down-time. Therefore, a need exists for a water spray nozzle that can be quickly and effectively unclogged should such clogging occur.
Several methods have been generally employed to control clogging of water spray systems. One method is to remove foreign substances or contaminants from the water prior to their introduction into a water nozzle. A second method is to bypass the foreign material away from the spray nozzle prior to entry therein, while, a third method is to employ nozzles having configurations that reduce clogging even if contaminants, either airborne or water entrained, should reach the nozzle.
Effective but expensive systems have been developed to remove particles from water. One system, developed by the U.S. Bureau of Mines and described in "Bureau of Mines Information Circular IC 8727", 1976, employs an inline Y-strainer that acts as a coarse strainer to remove large particles greater than about 1/8" in size, a hydrocyclone-type separator to remove and store almost all particles less than 1/8" in size and, finally, a particle filter to remove fine particles. That system virtually prevents clogging when maintained in proper operating condition. However, a drawback is that the cost of that system is relatively expensive.
The second, bypass method of controlling clogging employs a large spray manifold in the fluid path, just before the water reaches the nozzle. The manifold provides a container where particulates can settle just before they reach the nozzle. Occasional flushing of the manifold is necessary to remove accumulated, collected foreign material. This system is less costly than the above-mentioned filtration system and can be reasonably effective.
The third method of controlling clogging under circumstances where particles are not removed from the water prior to reaching the spray nozzle is based on the fact that the nozzle clogging is inversely proportional to the size of the orifice through the nozzle. Also nozzles that allow water to enter the nozzle at an angle, or tangentially to the direction of water flow through the nozzle, just upstream of the nozzle orifice clog less frequently than those wherein the water enters generally co-linearly with the flow of the water through the nozzle. The tangential entry port imports a cyclone-type internal flow within the nozzle that helps to reduce clogging. Thus, the third method employs large water discharge ports and tangential water entry ports, both of which tend to reduce clogging.
Despite the effectiveness of these three methods of controlling nozzle clogging, the nozzles employed with these systems may still clog and under certain circumstances, such systems may not be adequately effective. Therefore, a simple and effective device is necessary to quickly alleviate clogged nozzle conditions when such clogging occurs.
A variety of water nozzles have been proposed, such as disclosed in U.S. Pat. No. 2,117,647 in which a jet cleaning device is shown for a nozzle having an axially displaceable plunger movable into the nozzle by the application of a force on the plunger. The force on the plunger opposes a biasing force applied by a spring that is interposed between the nozzle and the plunger. Cleaning of the nozzle is accomplished by first pushing the plunger into the nozzle and then rotating the plunger. Release of the force applied against the plunger causes the plunger to be withdrawn from the nozzle due to the biasing force of the spring. A disadvantage of this device is that cleaning involves a two-step process of pushing the plunger within the nozzle and then rotating the plunger within the nozzle.
U.S. Pat. No. 2,652,857 discloses a valve for dispensing volatile substances such as resins, waxes and paints. The valve is opened by depressing a button against the biasing force of a spring to retract a valve member from a nozzle to allow fluid to flow through the valve and nozzle. Successive operation of the button moves the valve member into and out of the nozzle to generate a cleaning action of the sidewalls of the nozzle. This device has the disadvantage that cleaning action occurs only through successive movement of the valve member into and out of the nozzle.
U.S. Pat. No. 3,059,857 discloses a windshield washer system. One embodiment of the system includes a housing with an orifice through which an axially displaceable nozzle projects to discharge windshield washer solution. The nozzle is axially advanced through the orifice by the pressure of windshield washer fluid against the nozzle. Such advancement clears foreign substances that may be positioned within the orifice, however, such nozzle advancement cleans only foreign substances in the orifice but not foreign substances that may be present within the nozzle itself.
In a second embodiment of the invention, shown in U.S. Pat. No. 3,059,857, the housing supports a needle valve and a nozzle. The needle valve projects within an orifice of the nozzle when the nozzle is closed and no washer fluid is being dispensed thereby sealing the nozzle. When windshield washer solution is directed to the nozzle, the nozzle is axially advanced away from the needle valve thereby allowing discharge of the solution through and from the nozzle. Removal of the washer solution pressure from the nozzle causes the nozzle to be returned to a sealing position by a force applied by a biasing spring connected to the nozzle wherein the needle valve again seals the nozzle by projecting through the nozzle orifice. Return of the nozzle to the sealing position, thereby causing the needle valve to be projected through the nozzle, cleans foreign substances from the orifice of the nozzle. The washer solution discharge end of the nozzle is sealed from the housing by a flexible membrane extended between the movable nozzle end and the housing.
This embodiment shown in the above patent has the disadvantage that the membrane is flexed, or bent, each time the nozzle is axially advanced or returned due to relative movement between the nozzle and housing. Such regular bending may lead to early failure of the membrane due to fatigue. Further, such membranes may be susceptible to deterioration due to chemical exposure from the ambient atmosphere.
In a third embodiment of the invention shown in U.S. Pat. No. 3,059,857, the membrane between the housing and the nozzle is eliminated and scraping elements are attached to the nozzle to clean the interior of the housing as the nozzle is advanced from and returned toward the housing. These elements do not, however, clean the interior of the nozzle itself. Overall, with each of the above described embodiments the cleaning action occurs only when a change in fluid pressure within the housing causes the nozzle to move. Consequently, a disruption to the flow of fluid from the nozzle due to the changes in fluid pressure may occur during cleaning.
U.S. Pat. No. 3,474,968 discloses a self-cleaning nozzle that is axially movable into and out of the housing supporting the nozzle. The pressure of the fluid that is discharged from the nozzle controls the movement of the nozzle into and out of the housing. The nozzle is a generally hollow, cylindrical body having a sidewall defining one or more slits. The fluid to be discharged from the nozzle enters the nozzle through the slits and exits through an open end of the nozzle. A spider member, having projections that extend into the slits of the nozzle, is attached to the housing so as the nozzle moves into and out of the housing, any foreign substances that may be caught within the slits of the nozzle will be cleared.
A disadvantage with the device shown in U.S. Pat. No. 3,474,968 is that nothing is provided to clear the interior of the nozzle itself should a foreign substance pass through the slits and into the nozzle since the only cleaning action is provided by the slits in the side of the nozzle. Further, cleaning takes place only when a change in fluid pressure in the housing causes the nozzle to move. Again, a disruption to the fluid flow from the nozzle may occur as the result of changing fluid pressure during cleaning.
U.S. Pat. No. 4,223,838 discloses a self-flushing flow emitter for a drip irrigation system. The emitter includes a nozzle assembly having a nozzle and an axially displaceable rod which moves within the fluid discharge port of the nozzle in response to fluid pressure within the port. An increase in the fluid pressure causes the rod to advance further into the port while a decrease in pressure causes the rod to retract from the port under the influence of the force of a biasing spring. The advancement and retraction of the rod into and out of the port serves to clean the port. A disadvantage of this device is that cleaning takes place only when a change in fluid pressure in the housing causes the nozzle to move. Again, a disruption to the fluid flow from the nozzle may occur as the result of changing fluid pressure during cleaning.
U.S. Pat. No. 4,396,044 discloses a rinsing apparatus for cleaning filling elements of a filling machine. A filling element includes an axially displaceable rod that acts as a valve to open and close the filling element. The rod protrudes from the fluid discharge end of the filling element by an amount equal to the displacement of the valve between its open and closed position. Axial movement of the rod into the interior of the filling element causes the valve to open and allow fluid to be discharged from the fluid discharge port. The filling element is cleaned by opening the valve and introducing steam into the filling element.
U.S. Pat. No. 4,480,789 discloses a water nozzle for dust suppression. The device includes a water nozzle housing with an axially displaceable rod and piston assembly that is movable in one direction under the influence of water pressure within the nozzle and in the opposite direction under the influence of a biasing spring. Axial movement of the piston acts to clean a portion of the nozzle. However, even when the rod and piston assembly is advanced by the water pressure, the piston does not extend fully into the nozzle. Therefore, the entire extent of the nozzle is not cleaned by the rod and piston action. Further, movement of the piston is in response to variations in water pressure within the nozzle, thus, cleaning takes place only when a change in fluid pressure in the housing causes the nozzle to move. Again, a disruption to the fluid flow from the nozzle may occur as the result of changing fluid pressure during cleaning.
U.S. Pat. No. 4,629,120 discloses a self-cleaning atomizer nozzle assembly. The nozzle assembly includes a rod that extends through a fluid discharge port of a nozzle when the nozzle is axially displaced towards the rod by an axial force applied to a knob that is connected to the nozzle. The device is primarily adapted for the permanent mounting in the wall of a shower and has the disadvantage that the same knob that is employed for axially moving the nozzle relative to the rod for cleaning also is employed for adjusting the spray pattern of the nozzle through rotation of the knob. Therefore, it is possible that the control may be inadvertently rotated, thereby affected the spray pattern of the nozzle, even though the only intention was to momentarily axially advance the nozzle for cleaning only.
While a number of solutions have been proposed for cleaning a nozzle of particulate matter that becomes lodged in the outlet of the nozzle, the known device requires a change in the fluid pressure in the nozzle housing to move the nozzle. A disruption of the fluid flow through the nozzle is required to generate a fluid pressure differential. Therefore, there is a need to provide a self-cleaning nozzle that facilitates removing particulate matter clogging the nozzle without disrupting operation of the nozzle to generate the desired spray.